The present invention relates to a photosensitive resin composition which can be used for the interlayer dielectrics of semiconductor devices and for buffer coat films, xcex1-ray shielding films and the like, and which can form patterns by exposing to actinic radiation and dissolving away the exposed regions with aqueous alkali solution.
Heat-resistant resins such as polyimides are employed in the semiconductor field to form interlayer dielectrics, buffer coat films, xcex1-ray shielding films and the like. In using a polyimide in such applications, patterning of the polyimide film is necessary for the purpose of through hole formation and the like. For example, a solution of the polyamic acid, which is the polyimide precursor, is applied to the substrate, and then converted to the polyimide by heat treatment, after which a positive photoresist relief pattern is formed on the polyimide film and, with this as a mask, patterning is carried out by selective etching of the polyimide film by means of a hydrazine etching agent. However, this method has the problem that, as well as the process being complex since it includes the photoresist application and removal steps, etc, dimensional accuracy is lowered because of side etching. For such reasons, photosensitive resin compositions have been investigated which are heat-resistant resins, or precursors which can be converted to heat-resistant resins by means of a heat treatment or the like, and which themselves can undergo pattern processing.
For photosensitive resin compositions to have a pattern accuracy enabling them to be employed in passivation layer pattern formation, a method has been investigated whereby first of all patterning and curing of the photosensitive resin precursor composition is carried out on the passivation layer prior to pattern formation and then, with this pattern as a mask, dry etching of the underlying passivation layer is carried out (the one mask process). In accordance with this method, it is possible to shorten the process required in passivation layer pattern formation, leading to a reduction in costs.
When using a photosensitive resin composition, normally application and drying on the substrate are performed in the solution state, and irradiation with active light rays is performed through a mask. As negative-working photosensitive resin precursor compositions where the exposed regions are left following the developing, there are known compositions where a substance having carbon-carbon double bond which is demeriziable or polymerizable by actinic radiation and an amino group or quaternized salt thereof are added to a polyamic acid (JP-B-59-52822). compositions where an acrylamide is added to the polyamic acid (JP-A-3-170555) and compositions where a polyimide precursor with a carbon-carbon double bond, a specified oxime compound and a sensitising agent are incorporated (JP-A-61-118423). However, there is the problem that changing over from a conventional non photosensitive resin composition patterning process using a positive-working photoresist to a process using a negative-working photosensitive resin composition requires a change in the exposure device mask and a change in the developing equipment. Furthermore, these negative-working photosensitive resin compositions employ organic solvents in the developing, but from the point of view of preventing environmental pollution and improving the working environment, a photosensitive material which can be developed with an aqueous developer liquid instead of an organic developer liquid is desirable. For these reasons, alkali-developable positive-working photosensitive resin compositions are being investigated.
As known examples of positive-working photosensitive resin compositions where the exposed regions are dissolved away by developing with an aqueous alkali solution, there are the polyimide precursors where o-nitrobenzyl groups have been introduced by ester bonds (JP-A-60-37550), the composition where an o-quinone diazide compound is mixed into a polyamic acid ester (JP-A-2-181149), the composition where an o-quinone diazide compound is mixed with a polyamic acid or polyamic acid ester which has a phenolic hydroxyl group (JP-A-3-115461), the composition where an o-quinone diazlde compound is mixed with a polyimide which has a phenolic hydroxyl group (JP-3-177455), and the composition where an o-quinone diazide compound is mixed with a polyhydroxyamide (JP-B-1-46862) .
However. the polyimide precursors with o-nitrobenzyl groups introduced by means of ester bonds have the problem that the sensitising wavelengths are mainly below 300 nm and the sensitivity is low. In the case where an o-quinone diazide compound is mixed into the polyamic acid ester, the rate of dissolution by the alkali developer is low, so the sensitivity is low and the developing time is lengthy. In the case where an o-quinone diazide compound is added to a polyamic acid with a phenolic hydroxyl group, the solubility in the alkali developer is too great, so there is the problem that only dilute developer liquid can be employed and, since the unexposed regions are swollen by the developer liquid, fine patterning is difficult. Where an o-quinone diazide compound is mixed with a or polyimide with a phenolic hydroxyl group, the dissolution rate in the alkali developer is improved but there is the problem that further adjustment of the dissolution rate is difficult Where an o-quinone diazide compound is mixed with a polyhydroxyamide, the dissolution rate in the alkali developer is improved but there is the problem that change to the polymer composition is required for further adjustment in the dissolution rate. The present invention has been made in view of these various problems of the prior art, and it has as its objective to offer a photosensitive resin composition where adjustment of the dissolution time in the aqueous alkali solution is possible and, furthermore, where the polymer transparency is high at the exposure wavelengths and which has high sensitivity.
The present invention is a positive-working photosensitive resin composition which is characterized in that it contains (a) polymer in which the chief component comprises structural units of the kind where the bonding between structural units is represented by general formula (1) and (b) photoacid generator, and which can form a pattern by light irradiation and subsequent developing, and the total carboxyl groups contained in 1 g of said polymer is from 0.02 to 2.0 mmol. 
(R1 is an organic group of valency from 3 to 8 having at least 2 carbon atoms, R2 is an organic group of valency from 2 to 6 having at least 2 carbon atoms, R3 is hydrogen or an organic group with from 1 to 10 carbons but it is not all hydrogen. n is an integer of value from 3 to 100,000, m is 1 or 2, p and q are integers of value from 0 to 4 and p+q greater than 0).
In the present invention, the polymer represented by general formula (1) is preferably one which can form a polymer with imide rings, oxazole rings or other cyclic structures by heating or by means of a suitable catalyst. By forming cyclic structures, the heat resistance and solvent resistance are markedly enhanced. The polymer in which structural units represented by aforesaid general formula (1) are the chief component preferably has hydroxyl groups. In such circumstances, because of the presence of the hydroxyl groups, the solubility in aqueous alkali solution is better than that of a polyamic acid which does not have hydroxyl groups. In particular, from amongst hydroxyl groups, phenolic hydroxyl groups are preferred in terms of their solubility in aqueous alkali solution.
The residual group which constitutes R1 in general formula (1) denotes an acid structural component, and this acid component is preferably a C2 to C60 trivalent to octavalent group containing an aromatic ring and having from one to four hydroxyl groups. Where R1 does not contain hydroxyl groups, desirably the R2 component contains from one to four hydroxyl groups. An example is shown by general formula (6). 
(R7 and R9 represent C2 to C20 organic groups of valency 3 or 4, R8 represents a hydroxyl group-containing C3 to C20 organic group of valency from 3 to 6,and R10 and R11 are each hydrogen or a C1 to C10 monovalent organic group. R10 and R11 are not all hydrogen atoms, nor are they all C1 to C10 monovalent organic groups. r and t represent the integers 1 or 2, and s denotes an integer of value from 1 to 4).
Furthermore, the hydroxyl groups are preferably in a position adjacent to an amide bond. As examples thereof, there are structures of the kind shown in (10) below, but the present invention is not restricted to these. 
(R is a hydrogen atom or a C1 to C20 monovalent organic group)
Furthermore, for R1, it is also possible to employ tetracarboxylic acids, tricarboxylic acids and dicarboxylic acids which do not contain hydroxyl groups. As examples thereof, there are aromatic tetracarboxylic acids such as pyromellitic acid, benzophenonetetracarboxylic acid, biphenyltetracarboxylic acid, diphenyl ether tetracarboxylic acid and diphenyl sulphone tetracarboxylic acid, and the diesters thereof where two of the carboxyl groups are converted to methyl ester or ethyl ester group form; aliphatic tetracarboxylic acids such as butane tetracarboxylic acid and cyclopentane tetracarboxylic acid, and the diesters thereof where two of the carboxyl groups are in the methyl or ethyl group form; and aromatic tricarboxylic acids such as trimellitic acid, trimesic acid, naphthalene tricarboxylic acid and the like.
The residual group which constitutes R2 in general formula (1) denotes a diamine structural component. Preferred examples of R2 are those with an aromatic ring, from the point of view of the heat resistance of the polymer obtained, and also having from one to four hydroxyl groups. Where R2 does not have hydroxyl groups, it is desirable that the R1 component contain from one to four hydroxyl groups. Furthermore, the hydroxyl groups are preferably positioned adjacent to an amide bond.
As specific examples, there are compounds such as bis(aminohydroxyphenyl)hexafluoropropane, diaminodihydroxypyrimidine, diaminodihydroxypyridine, hydroxydiaminopyrimidine, diaminophenol and diaminodihydroxybenzene, and those with the following residual structures. 
(i is an integer in the range 1 to 4, j and k are integers in the range 0 to 4, and j+k is at least 1).
Amongst these R2 components, as further preferred examples there can be cited the compounds with the structures shown by general formulae (7), (8) and (9). Of these, specific examples of further preferred structures are exemplified by general formulae (11), (12) and (13). 
(R12 and R14 represent hydroxyl group-containing C2 to C20 organic groups of valency 3 or 4, and R13 represents a C2 to C30 divalent organic group. u and v represent the integers 1 or 2). 
(R15 and R17 represent 2 to C30 divalent organic groups, and R16 represents a hydroxyl group-containing C2 to C20 organic group of valency 3 to 6. w represents an integer in the range 1 to 4). 
(R16 represents a C2 to C30 divalent organic group, and R19 represents a hydroxyl group-containing C2 to C20 organic group of valency 3 to 6. x represents an integer in the range 1 to 4). 
Furthermore, it is also possible to use a diamine which does not contain a hydroxyl group for the residual group containing R2 in general formula (1). As examples thereof, there are phenylenediamine, diaminodiphenyl ether, aminophenoxybenzene, diaminodiphenylmethane, diamlinodiphenylsulphone, bis(trifluoromethyl)benzidine, bis(aminophenoxyphenyl)propane, bis(aminophenoxyphenyl)sulphone or compounds comprising these aromatic rings with alkyl group and/or halogen atom substituents, and aliphatic cyclohexyldiamine, methlylene biscyclohexylamine and the like. These diamine compounds can be used on their own or they can be used in combinations of two or more types. It is preferred that they be used as no more than 40 mol % of the diamine component. If more than 40 mol % is copolymerized then the heat resistance of the polymer obtained is lowered.
With the objective of improving the adhesion to the substrate, it is also possible to use a diamine compound with a siloxane structure within a range such that the heat resistance is not lowered. As examples of diamines with a siloxane structure, there may be used bis(3-aminopropyl)tetramethyldisiloxane, bis(3-aminopropyl)tetraphenyldisiloxane, bis(4-aminophenyl)tetramethyldisiloxane and the like.
R3 in general formula (1) represents hydrogen or a C1 to C10 organic group. If the number of carbons in R3 exceeds 20 then the solubility in aqueous alkali is lost. In terms of the stability of the photosensitive resin solution obtained, R3 is preferably an organic group, but hydrogen is preferred in terms of the solubility in aqueous alkali. In other words, it is not desirable that R3 all be hydrogen or that it all be an organic group. By adjusting the proportion of R3 which comprises hydrogen or which comprises an organic group, the dissolution rate in aqueous alkali solution may be varied, so by such adjustment it is possible to obtain a photosensitive resin composition with a suitable dissolution rate. Thus, the carboxyl group content of the polymer is preferably from 0.02 mmol to 2.0 mmol per 1 g of polymer. More preferably, it is from 0.05 mmol to 1.5 mmol. If there is less than 0.02 mmol, then the solubility in the developer liquid is too low, while if there is more than 2.0 mmol then it is not possible to realise a difference in dissolution rate between the exposed and unexposed regions. m represents 1 or 2, and p and q are each integers in the range 0 to 4, with p+q greater than 0. If p is 5 or more, then the properties of the heat-resistant resin film obtained are impaired.
Again, it is possible to control the amount of residual carboxyl groups by imidization of some of the carboxyl groups. As the method of imidization, any known imidization method can be used. The proportion of the imidization at this time is preferably from 1% to 50%. If the percentage imidization exceeds 50%, then the absorption by the polymer of the actinic radiation used for exposure is increased and the sensitivity decreased.
The polymer represented by general formula (1) is preferably as transparent as possible in terms of the actinic radiation used for exposure. Hence, the absorbance of the polymer at 365 nm is preferably no more than 0.1 per 1 xcexcm of film thickness. More preferably, it is no more than 0.08.If it is more than 0.1, then the sensitivity in terms of exposure to 365 nm actinic radiation is lowered.
The positive-working photosensitive resin of the present invention may only comprise structural units represented by general formula (1), or it may comprise a copolymer with other structural units or a blend. In such circumstances, the content of the structural units represented by general formula (1) is preferably at least 90 mol %. The type and amount of structural units employed for copolymerisation or blending are preferably selected from within a range such that the heat resistance of the polyimide polymer obtained by the final heat treatment is not impaired. Generally speaking, the polymer represented by general formula (1) can be obtained by treating the carboxyl groups in a polymer represented by general formula (2) by means of a compound represented by general formula (3), (4) or (5). 
(R1 is 3-valent to 8-valent organic group with at least 2 carbons, and R2 is a 2-valent to 6-valent organic group with at least two carbon atoms. n is an integer in the range 3 to 100,000, m is 1 or 2, p and q are each integers in the range 0 to 4 and p+q greater than 0. 
The polymer chiefly comprising structural units represented by general formula (2) in the present invention is synthesized by known methods. For example, it can be synthesized by the method of reacting a tetracarboxylic dianhydride and a diamine compound at low temperature (C. E. Sroog et al, J. Polymer Science, Part A-3, 1373 (1965)).
In general formula (3), R4 and R5 represent a hydrogen atom or a monovalent organic group, nitrogen-containing organic group or oxygen-containing organic group with at least one carbon. R4 and R5 may be the same or different. R6 represents a monovalent organic group with at least one carbon.
R6 in general formula (3) or in general formula (4) represents a monovalent organic group with at least one carbon and R7 represents a divalent organic group, nitrogen-containing organic group or oxygen-containing organic group with at least one carbon. Specifically, in the case of the compounds represented by general formula (3), examples are N,N-dimethylformamide dimethyl acetal, N,N-dimethylformamide diethyl acetal, N,N-dimethylformamide dipropyl acetal, N,N-dimethylformamide dibutyl acetal, N,N-dimethylformamide dibenzyl acetal, N,N-dimethylformamide bis[2-(trimethylsilyl)ethyl]acetal, N,N-dimethylacetamide diethyl acetal, trimethyl orthoformate, triethyl orthoformate, trimethyl orthoacetate, triethyl orthoacetate, trimethyl orthobutyrate, triethyl orthobutyrate, trimethyl orthobenzoate, triethyl orthobenzoate, 1,3-dimethylimidazolidinone dialkyl acetal, ethylene carbonate dialkyl acetal, propylene carbonate dialkyl acetal and the like, with N,N-dimethylformamide dimethyl acetal, N,N-dimethylformamide diethyl acetal, N,N-dimethylformamide dipropyl acetal, N,N-dimethylformamide dibutyl acetal and N,N-dimethylformamide dibenzyl acetal preferred.
As examples of the compounds represented by general formula (4), R7 represents a divalent organic group which forms a ring. Preferred examples of the compounds represented by general formula (4) are N-methylpyrrolidone dimethyl acetal, N-methylpyrrolidone diethyl acetal N-methylpyrrolidone dipropyl acetal, N-methylpyrrolidone dibutyl acetal, xcex3-butyrolactone dimethyl acetal, xcex3-butyrolactone diethyl acetal and the like. As specific examples of the compounds represented by general formula (5), there are methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether. tert-butyl vinyl ether, cyclohexyl vinyl ether and the like, but there is no restriction to these. Preferably. tert-butyl vinyl ether, cyclohexyl vinyl ether and isopropyl vinyl ether are used.
At the time of the esterification treatment of the polymer represented by general formula (2) by means of general formula (3), general formula (4) or general formula (5), imidization may also take place as a side reaction but the proportion of imidization in terms of the esterification reaction can be suppressed by selection of the reaction conditions, namely by selection of the reaction solvent and the reaction temperature, etc.
As the reaction solvent, there is preferably used N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, 1,3-dimethylimidazolidinone, hexamethylphosphoramide, xcex3-butyrolactone or other such non-protic polar solvent, with N-methyl-2-pyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide more preferred. As solvents other than these, there can be used, in total or in part, ketone solvents such as acetone or methyl ethyl ketone, alcohol solvents such as methanol or ethanol, or ester solvents such as propylene glycol monomethyl ether acetate, ethyl lactate or the like. The esterification reaction temperature lies in the range from 0xc2x0 C. to 150xc2x0 C., preferably 20xc2x0 C. to 100xc2x0 C. and more preferably 3xc2x0 C. to 80xc2x0 C. If the reaction temperature is less than 0xc2x0 C., then the time for the reaction to reach completion is prolonged and so this becomes impractical. Furthermore, when the reaction temperature exceeds 150xc2x0 C., problems readily arise such as the extent of imidization increasing, the polymer transparency falling and a gel component being produced. In the treatment by means of a compound represented by general formulae (3) or (4) it is possible, for the purpose of accelerating the reaction, to employ from 0.01 to 10 mol % of an acid such as trifluoroacetic acid, p-toluenesulphonic acid or methanesulphonic acid, or of a base such as triethylamine, pyridine or the like.
At the time of the reaction between the polymer represented by general formula (2) and a compound represented by general formula (3), (4) or (5), there may also be added an acid compound as a catalyst for accelerating the reaction. With regard to the amount of such acid compound added, for the purposes of selectively accelerating the reaction there can be used from 0.01 to 10 mol % in terms of the carboxyl groups. As specific examples of the acid catalyst there are hydrochloric acid, sulphuric acid, nitric acid, phosphoric acid, oxalic acid and the like, but there is no restriction to these. Preferably, there is used high pKa value phosphoric acid or oxalic acid. This is thought to be because the higher the pKa value of the acid catalyst the greater the nucleophilic character of the counter anion produced, and cationic polymerisation is suppressed.
The amount of the compound represented by general formula (3), (4) or (5) added can be determined from the concentration of the carboxyl groups in the polymer represented by general formula (2).
The compounds represented by general formulae (3), (4) and (5) may be used on their own or they may be used as mixtures of a plurality thereof.
As an alternative thereto for esterification of the carboxyl groups, it is possible to use the method of converting the carboxylic acid to the metal salt and subjecting this to the action of an alkyl halide, the method of using diazomethane, or the reaction based on dialkyl sulphate, etc.
The preferred reaction solvent is N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, 1,3-dimethylimidazolidinone, hexamethylphosphoramide, xcex3-butyrolactone or other such non-protic polar solvent, with N-methyl-2-pyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide further preferred. The reaction temperature lies in the range from xe2x88x9210xc2x0 C. to 150xc2x0 C., preferably 0xc2x0 C. to 80xc2x0 C. and more preferably 10xc2x0 C. to 60xc2x0 C. If the reaction temperature is below xe2x88x9210xc2x0 C., the time for the reaction to reach completion is prolonged and so it becomes impractical. Again, if the reaction temperature exceeds 150xc2x0 C., problems arise due to reactions such as imidization, a reduction in the polymer transparency, the formation of a gel component and a lowering of the cured film properties.
Treatment of the polymer represented by general formula (2) by the compounds represented by general formulae (3), (4) or (5) is carried out by mixing and stirring general formula (3), (4) or (5) and, optionally, an acid catalyst, with a solution of general formula (2) dissolved in an organic solvent. In the case where the solvent used at the time of the synthesis of the polymer represented by general formula (2) and the solvent used when treating the polymer with general formula (3) and the acid catalyst compound are the same, then said treatment can be carried out by mixing and stirring the compound of general formula (3), (4) or (5) with the solution obtained following polymerisation.
As examples of the photoacid generator employed in the present invention, there are compounds which are decomposed and generate acid by irradiation such as diazonium salts, diazoquinone sulphonamides, diazoquinone sulphonic acid esters, diazoguinone sulphonates, nitrobenzyl esters, onium salts, halides, halogenated isocyanates, triazine halides, bisarylsulphonyldiazomethanes, disulphones and the like. In particular, o-quinone diazide compounds are preferred since they have the effect of suppressing the water solubility of the unexposed regions. Such compounds include 1,2-benzoquinone-2-diazido-4-sulphonate ester or sulphonamide, 1,2-naphthoquinone-2-diazido-5-sulphonate ester or sulphonamide, 1,2-naphthoquinone-2-diazido-4-sulphonate ester or sulphonamide, and the like. These can be obtained for example by a condensation reaction between an o-quinonediazide sulphonyl chloride such as 1,2-benzoquinone-2-azido-4-sulphonyl chloride, 1,2-naphthoquinone-2-diazido-5-sulphonyl chloride or 1,2-naphthoquinone-2-diazido-4-sulphonyl chloride, and a polyhydroxy compound or polyamine compound in the presence of a dehydrochlorination catalyst.
As examples of the polyhydroxy compound, there are hydroquinone, resorcinol, pyrogallol, bisphenol A, bis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxyphenyl)hexafluoropropane, 2,3,4-trihydroxybenzophenone, 2,3,4,4xe2x80x2-tetrahydroxybenzophenone, 2,2xe2x80x2,4,4xe2x80x2-tetrahydroxybenzophenone, tris(4-hydroxyphenyl)methane, 1,1,1-tris(4-hydroxyphenyl)ethane, 1-[1-(4-hydroxyphenyl)isopropyl]-4-[1,1-bis(4-hydroxyphenyl)ethyl]benzene, methyl gallate, ethyl gallate and the like.
As examples of the polyamine compounds there are 1,4-phenylenediamine, 1,3-phenylenediamine, 4,4xe2x80x2-diaminodiphenyl ether, 4,4xe2x80x2-diaminodiphenylmethane, 4,4xe2x80x2-diaminodiphenylsulphone, 4,4xe2x80x2-diaminodiphenylsulphide and the like.
As polyhydroxypolyamine compounds, there are 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 3,3xe2x80x2-dihydroxybenzidine and the like.
Preferably from 5 to 100 parts by weight, and more preferably from 10 to 40 parts by weight, of the o-quinone diazide compound is mixed per 100 parts by weight of the polymer represented by general formula (1). With less than 5 parts by weight, insufficient sensitivity is obtained, while with more than 100 parts by weight there is the possibility that the heat resistance of the resin composition will be lowered.
The positive-working photosensitive resin composition of the present invention is preferably employed in the solution state by dissolving the polymer represented by general formula (1), which is obtained by treating polymer represented by general formula (2) with a compound represented by general formula (3), (4) or (5), in a solvent along with the photoacid generator As the solvent, non-protic polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, 1,3-dimethylimidazolidinone, hexamethylphosphoramide and xcex3-butyrolactone may be used on their own, or in combinations of two or more thereof, but other solvents can also be used providing that they will dissolve the polymer represented by general formula (1) and the photosensitizer.
Again, where required, with the objective of enhancing the application properties between the photosensitive precursor composition and the substrate, there may also be mixed therein surfactants, esters such as ethyl lactate and propylene glycol monomethyl ether acetate, alcohols such as ethanol, ketones such as cyclohexanone and methyl isobutyl ketone, and ethers such as tetrahydrofuran and dioxane Again, it is possible to add inorganic particles such as silicon dioxide and titanium dioxide, or polyimide powder, etc.
Furthermore, in order to enhance the adhesion to an underlying substrate such as a silicon wafer, it is possible to add from 0.5 to 10 parts by weight of a silane coupling agent, titanium chelating agent or the like to the photosensitive resin composition varnish, or the underlying substrate may be pretreated with such a chemical.
When added to the varnish, from 0.5 to 10 parts by weight of the silane coupling agent, such as methyl methacryloxydimethoxysilane or 3-aminopropyltrimethoxysilane, or of the titanium chelating agent or aluminium chelating agent is added in terms of the polymer in the varnish.
When treating the substrate, a solution obtained by dissolving 0.5 to 20 parts by weight of the aforesaid coupling agent in a solvent such as isopropanol, ethanol, methanol, water, tetrahydrofuran, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, ethyl lactate, diethyl adipate or the like is used to treat the surface by spin coating, immersion, spray application or vapour treatment, etc. Depending on the circumstances, by subsequent application of temperature in the range 50xc2x0 C. to 300xc2x0 C., reaction between the substrate and the coupling agent is promoted.
Next, explanation is provided of the method of forming a heat-resistant resin pattern using the photosensitive resin composition of the present invention.
The photosensitive resin composition of the present invention is applied onto the substrate. As the substrate, there may be used a silicon wafer, a ceramic, gallium arsenide or the like, but there is no restriction to these. The application method may be rotary application using a spinner, spray application, roll coating or the like. Furthermore, the applied film thickness will differ with the application means, the solids content of the composition and the viscosity, etc, but normally application is performed such that the film thickness after drying is from 0.1 to 150 xcexcm.
Next, the photosensitive resin composition coating is obtained by drying the substrate on which the photosensitive resin composition has been applied. The drying is preferably carried out using an oven, hot plate or infrared radiation, etc, for from 1 minute to several hours within the range 50xc2x0 C. to 150xc2x0 C.
Subsequently, this coating is irradiated with actinic radiation through a mask with the desired pattern, and exposure effected. Examples of the actinic radiation employed for the exposure are ultraviolet light, visible light, an electron beam, X-rays and the like, but it is preferred in the present invention that there be used the mercury lamp i-line (365 nm), h-line (405 nm) or g-line (436 nm).
To form the heat-resistant resin pattern, the exposed regions are eliminated using a developer liquid following the exposure. Preferred examples of the developer liquid are aqueous tetramethylammonium hydroxide solutions, and aqueous solutions of compounds which exhibit alkalinity such as diethanolamine, diethylaminoethanol, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, triethylamine, diethylamine, methylamine, dimethylamine, dimethylaminoethyl acetate, dimethylaminoethanol, dlmethylaminoethyl methacrylate, cyclohexylamine, ethylenediamine, hexamethylenediamine and the like. Further, depending on the circumstances, there may be added to such aqueous alkali solutions a non-protic polar solvent such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, xcex3-butyrolactone or dimethylacrylamide, an alcohol such as methanol, ethanol or isopropanol, an ester such as ethyl lactate or propylene glycol monomethyl ether acetate, a ketone such as cyclopentanone, cyclohexanone, isobutyl ketone or methyl isobutyl ketone, or a combination of more than one such solvent. After developing, a rinsing treatment is carried out with water. The rinsing treatment may also be carried out with the addition, to the water, of an alcohol such as ethanol or isopropyl alcohol, ester such as ethyl lactate or propylene glycol monomethyl ether acetate, or carbon dioxide, hydrochloric acid, acetic acid or other such acid.
Following the developing, by application of a temperature of from 200xc2x0 C. to 500xc2x0 C. conversion is effected to the heat-resistant resin coating. This heat treatment is carried out for from 5 minutes to 5 hours either by selection of temperatures and raising the temperature in stepwise fashion, or by selecting a temperature range and continuously raising the temperature. As an example, heat treatment is carried out for 30-minute periods at 130xc2x0 C., 200xc2x0 C. and 350xc2x0 C. Alternatively, there is the method of linearly increasing the temperature over two hours from room temperature to 400xc2x0 C.
The heat-resistant resin coating formed by means of the photosensitive resin composition of the present invention may be used in applications such as semiconductor passivation layers, semiconductor device protective films and the interlayer dielectrics of multilayer interconnects for high density mounting, etc.